Every AD assassin's winrate drastically dropped in S15
Qiyana's winrate dropped most of all and she's still positive winrate despite probably being in the worst state since she was released. This shows you how strong the pick is in high elo, despite how laughable her damage is, the utillity and CC she provides is extremely valuable and she's still playable (although not particularly rewarding)
Imo the reason Assassins got way worse this season is most likely them having bad waveclear and low tempo compared to other midlaners. Oneshotting waves asap as a mage allows you to basically avoid the entire laning phase vs an assassin. With minions dying faster now and fights taking places all the time, ideally you want to pick a champ that can clear waves as fast as possible from long range in order to move to the fight as quick as possible (Having prio). Realistically as an assassin you are stuck under tower, moving 5-10 seconds later than the enemy midlaner. Early game and snowball potential used to be the strongside of Assassins but they're simply too weak right now. The damage is just not there. When you pick a midlane assassin it feels like your champion is as weak as an immobile artillery mage in the early game, and way weaker than meta champs like Viktor, Orianna, Syndra which are lane bullies. You're also weaker in mid game and DRASTICALLY weaker in late-game. Assassins just don't scale anymore. Because of their itemisation being horrendous. Because your early game doesn't allow you to snowball. Because everyone is building survivabillity items/ getting naturally tanky due to inflated base hp/armor per lvl. Because despite spending a lot/most of their gold on survivabillity Tanks/Bruisers/Mages do way more damage than a glass-cannon Assassin who spends all his gold on damage items (and doesn't really have any good survivabillity options).
Eyeball collection removal basically means you lost 18 AD/30 AP in S15 as an assassin if you run Electro, which is the best keystone for most midlane assassins and basically mandatory on Qiyana right now. What you gained instead of eyeball collection is a useless utillity rune that does nothing for midlane assassins and belongs in inspiration rune tree. First strike used to be a good keystone option aswell, but it got SPECIFICALLY nerfed for asssassins (only God knows why).
I was hoping Riot would give assassins some power through items for a few months atleast, like they did during S14 split 1.
Serrated dirk used to give 10 more AD for the same gold cost.
Profane Hydra had an execute to it's active which allowed you to clear waves fast in order to atleast somewhat match Mage waveclear. It was also a lot of extra damage to champions for finishing them off.
Brutalizer used to atleast give you atleast 8 lethality, it got nerfed to 5. Rn it's probably unironically the worst component in the game.
Serylda's used to give you lethality and its armor pen scaled with lethality. It even used to slow in previous seasons. Well they removed all that for whatever reason.
Before S14 we used to be able to build BC+Serylda. Duskblade used to give you tons of haste, Eclipse was an actuall lethality assassin item meant for countering hp stacking. When it was tank meta and everyone was abusing armor items we had itemisation to counter that. No longer the case with current item system. Tanks can just walk upto you and oneshot you and there is absolutely nothing you can do. I understand Assassins aren't meant to be good vs tanks. The issue is every class is using tank items. Everyone is building Tabi's (T3 Tabis especially are a nightmare for assassins, good luck even breaking the shield, nevermind the insane amounts of armor). Mages get 1k hp shield from a scaling abillity power item that gives 25 haste and tons of mana. If you just compare Seraph's Embrace to any assassin item you will realise how unbalanced itemisation in this game is.
Tanks rn basically do way more burst dmg than an assassin with Heartsteel and Grasp. All that while having 10k HP and 200 armor, being able to facetank an entire team for 20+ seconds, providing tons of CC and being mechanically incredibly easy to play, whereas assassins are mechanically difficult, do less damage than tanks while being full glass cannon.
AP Assassins aren't that much better either, their items are just slightly less shit than AD assassins. They also have better damage numbers and scaling in their kits.
Overall if Riot doesn't do something about the Item system and disparity between different classes, S15 will be the biggest dissapointment in league's history. I don't even mind the changes they made, Feats of Strength, Attakan etc. I think it's alright to have more snowballing in the game. But these changes do absolutely nothing to fix the big issues with the game. Once again - Item system balancing and enormous disparity between different classes. I think AD assassins and to a lesser degree ADC are the classes that have significantly worse items than other classes rn.
We need a Item System Overhaul more than ever, new objectives and cool gimmicks are alright. But until Riot starts actually fixing game balancing the game will keep dying. It sucks to be able to play and enjoy the game 2-3 months out of the year if you're lucky because of disgustingly poor balancing.